1. Field of the Invention
The present invention relates to a touch switching apparatus, and more particularly, to a touch switching apparatus for clearly displaying a mark drawn on a touch unit when a user operates it by using a flat light emitting device as a backlight.
2. Description of the Background Art
Recently, in order to facilitate manipulation of electronic, electric or information instrument such as a TV receiver or a VCR and so forth, a touch switching apparatus is increasingly adopted to be installed in an operating panel of the instruments.
The touch switching apparatus performs ON/OFF operation when a part of the user""s body (i.e., fingers, etc.) contacts a touch unit and an electric charge accumulated in the body is inputted via the touch unit thereto. At this time, in order to indicate an operation state of the touch switching apparatus, a backlight is used inside the touch unit.
FIG. 1 is a sectional view of the touch switching apparatus using a light emitting diode (LED) as a backlight in accordance with a conventional art.
As shown in FIG. 1, the conventional touch switching apparatus includes a glass plate 1 being contacted by a body part of a user for manipulation; a touch unit (TS) arranged at predetermined positions of the glass plate 1; a conductive silver-plated film 3 partially plated with silver on the inner surface of the glass plate 1 or the opposite face of the touch pat (TS) corresponding to the touch unit (TS); a printed circuit board (PCB) 2 installed spaced apart from the glass plate 1; a conductive rubber 4 installed at the PCB 2 corresponding to the silver-plated film 3 of the glass plate 1; a pin plug 5 fixing the conductive rubber 4 to the PCB 2; and a light emitting diode (LED) 6 installed at the PCB 2 for emitting light when the silver-plated film 3 and the conductive rubber 4 are connected to each other as the user contacts the touch unit (TS).
The operation of the conventional touch switching apparatus using the LED as a backlight constructed as described above will now be explained.
When a body part of a user (i.e., fingers, etc.) touches the touch unit (TS) of the glass plate 1, the total capacitance by adding a capacitance of the glass plate 1 and a capacitance of the user""s body is inputted to an input terminal of a drive circuit unit (not shown) of the touch switching apparatus.
In detail, as the current generated by the total capacitance is applied through the conductive rubber 4 and the pin plug 5 to the drive circuit unit of the PCB 2, the drive circuit unit is operated and an LED of the touch unit emits light to the corresponding touch unit for a predetermined time period.
Accordingly, the user can recognize whether the touch unit touched by him or her has been operated or not.
However, the conventional touch switching apparatus using the LED 6 as a backlight has many problems.
For example, first, it fails to evenly illuminate light emitted by the LED 6 to a mark (for example, a symbol or a character) expressed at the touch unit of the glass plate 1.
That is, the touch unit with a symbol or a character is bright at its middle portion and is gradually darkened as it comes to its marginal portions of upper and lower and left and right sides, causing a problem that the operation state is not clearly shown.
Secondly, the light emitted from the LED 6 being operated illuminates also adjacent touch units (i.e., a symbol or a character) as well as the corresponding touch unit (i.e., a symbol or a character).
That is, since the glass plate 1 and the PCB 2 are distanced each other, the light emitted from one LED being operated also illuminates other touch units.
As a solution to the problem, the touch switching apparatus may be designed such that the touch units are formed to be so distant enough that one LED being operated may not affect other touch units or such that a light guide (or a light blocking unit) is installed to enable the light emitted from the LED to illuminate only its corresponding touch unit (i.e., a character or a symbol). In such a case, however, another problem arises that the touch switching apparatus is increased in size larger than that of the conventional ones.
Thirdly, since it uses the LED 6 as a backlight, the sizable LED 6 is to be installed standing upright on the PDB 2. In addition, since the conductive rubber is to be installed connected with the PCB 2 by using a pin plug, the touch switching apparatus is thick and sizable.
Therefore, an object of the present invention is to provide a touch switching apparatus that is capable of clearly displaying a mark drawn on a touch unit when operated by a user.
Another object of the present invention is to provide a touch switching apparatus that is capable of clearly displaying a mark drawn on the touch unit by evenly illuminating on the touch unit.
Still another object of the present invention is to provide a thin touch switching apparatus.
Yet another object of the present invention is to provide a touch switching apparatus using a flat light emitting device as a backlight.
Still yet another object of the present invention is to provide a touch switching apparatus using a thin flat light emitting device as a backlight.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a touch switching apparatus including: a switching unit for evenly illuminating on a touch unit manipulated by a user among touch units with marks; and a driving circuit for driving the switching unit when detecting the manipulation.
To achieve the above objects, there is also provided a touch switching apparatus including: an insulating unit for inducing a capacitance as a user""s body contacts and presented with a touch switch for manipulation of an instrument; a conductive unit for detecting a capacitance through the medium (dielectric) of a user""s body contacting the insulating unit; a flat light emitting device for providing a backlight to the insulating unit to visibly express a corresponding switching unit when a body contact is detected by the conductive unit; and a drive unit for detecting whether a switch has been manipulated according to a change in a capacitance made by the conductive unit;
To achieve the above objects, there is also provided a touch switching apparatus including a glass plate to which a capacitance is guided by being contacted with the body of a user, having a touch unit for instrument manipulation presented at the outer surface and a conductive plated film formed on the inner surface corresponding to the touch unit; an EL sheet operated by user""s manipulation, for illuminating light on the touch unit; a conductive rubber for detecting a change in a capacitance through the medium of a user""s body when the user""s body contacts the touch unit from a position corresponding to the touch unit; and a printed circuit board for detecting a change in a capacitance of the body contacted with the touch unit through the conductive rubber and determining whether the touch unit has been manipulated.